merged all the latest changes from 2.4 to trunk

samples/gpu/CMakeLists.txt

@@ -21,7 +21,7 @@ if(BUILD_EXAMPLES AND OCV_DEPENDENCIES_FOUND)
     ocv_include_directories(${CUDA_INCLUDE_DIRS})
   endif()
 
-  if(CMAKE_COMPILER_IS_GNUCXX)
+  if(CMAKE_COMPILER_IS_GNUCXX AND NOT ENABLE_NOISY_WARNINGS)
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-unused-function")
   endif()
 

samples/gpu/brox_optical_flow.cpp

@@ -215,7 +215,6 @@ int main(int argc, const char* argv[])
             switch (key)
             {
             case 27:
-                return 0;
                 break;
 
             case 'A':